59 
formities,” and “ designs,” is utterly diverse from what it was 
among the ideas which we have left. This is a matter of 
very great moment to the inquirer after truth. It reminds 
him that he ought never to confound ideas with things. He 
may take all the help that ideas can render ; but, after all, he 
must seek thoughts for himself, in the way of observing Nature, 
and also in that of sifting most carefully the observations and 
reasonings of others. 
When we pass from the teachings of Darwin to those of 
the equally celebrated Agassiz, the contrast of thought is 
very striking. Here “ species ” are no longer “ improved 
varieties 33 that have diverged from each other in the course 
of countless ages, and in their descent from a common 
parentage, but “primordial forms 33 Agassiz adopts the 
idea of Morton, and declares his full belief that species are 
thus “ primordial/* ** “ Species,” he says, “ are, then, distinct 
forms of organic life, the origin of which is lost in the 
primitive establishment of the state of things now existing; 
and varieties are such modifications of the species as may 
return to the typical form under temporary influences.” 
When lecturing to his associates, on his way to Brazil, he 
said , — “ I am often asked what is my chief aim in this 
expedition to South America ? No doubt, in a general way, 
it is to collect materials for future study. But the conviction 
which draws me irresistibly is, that the combination of animals 
on this continent, where the faunas are so characteristic and so 
distinct from all others, will give me the means of showing 
that the transmutation theory is wholly without foundation in 
fact.”t It was the full belief of Agassiz, when he had 
completed his journey, that his observations had more than 
established this conviction. There is great vigour in the 
faifch of this distinguished naturalist ; and hence the conflict of 
thought between those who think with Darwin and those 
who think with Agassiz is real and hearty. When putting 
the question as to whether there is any standard in nature 
by which species may be infallibly marked off from mere 
varieties, he says, — “ The true principle of classification exists 
in Nature herself, and we have only to decipher it.” Then he 
says , — “ The standard is to be found in the changes animals 
undergo, from their first formation in the egg to their adult 
condition.” J He notices the remarkable similarity in the 
embryological forms of widely differing species, and the use 
which a Darwinian is disposed to make of it. “'But,” says 
he, “ when we follow it out in the growth of the animals 
* See Types of Mankind, p. Ixxix., 1865. 
t Travels in Brazil, p. 33, 1868. % Ibid. pp. 20, 21. 
